In a typical motorized watercraft, the exhaust system includes an exhaust manifold elbow. The exhaust manifold elbow includes an exhaust gas passage and a water passage with the two passages juxtaposed. Exhaust gas from the engine exits the exhaust system through the exhaust gas passage. Water from the lake or ocean, injected into the exhaust system for cooling the running engine, passes near the exhaust gas passage, where it further cools the exhaust gas. The exhaust gas and cooling water exit the elbow mixing area of the exhaust manifold elbow and are mixed with each other. Ideally, both are then expelled.
In motorized watercraft, portions of the exhaust system can be immersed in the water (e.g., lake or ocean) while the engine is running. This arrangement may cause water to move back towards the engine through the gas passage. This is known as water reversion. Water reversion is undesirable for many reasons. Water in the engine may damage it. Water reversion may also decrease engine performance and increase fuel consumption since water moving upstream through the gas passage impedes the flow of exhaust exiting from the engine. In addition, reversion of cooling water may also occur to cause the above-mentioned problems, even in exhaust systems where the exhaust ejection point is not immersed in water so long as the system uses water for cooling the engine and/or exhaust gas.
Watercraft exhaust manufacturers have attempted several solutions to the problem of water reversion, such as placing a stationary, semi-perforated cap-like structure or a stationary plate in the exhaust manifold elbow area. While these attempted solutions may prevent some amount of water backflow, they also have the tendency to impede the flow of exhaust gas out of the exhaust system. Impeding exhaust gas flow decreases performance and increases fuel consumption.
Accordingly, it would be desirable to provide a device for controlling water reversion without decreasing engine performance or increasing fuel consumption.